1. Field of the Invention
The invention relates to a motive power transmission apparatus for a vehicle which transmits rotation power that is generated by a motive power source to an output side via a planetary gear device. In particular, the invention relates to a technology of supplying oil to such a planetary gear device.
2. Description of the Related Art
There have been motive power transmission apparatuses for vehicles which transmit rotation power generated by, for example, an electric motor, to wheels via a planetary gear device (e.g., see Japanese Patent Application Publication No. 2007-195320 (JP-A-2007-195320)).
Regarding a related-art technology according to Japanese Patent Application Publication No. 2007-195320 (JP-A-2007-195320), the abstract in the publication states “A geared motor 10G, obtained by disposing an electric motor 10 behind a speed reducing gear mechanism 11, is used as an in-wheel motor disposed at the lower part of a vehicle spring. The output shaft 10b of the electric motor 10 is made hollow to form an oil inlet path 15z, and a motor case 10a is housed in a cylindrical housing 10H to form a stator cooling path 10s. The stator cooling path 10s and the interior of the speed reducing gear mechanism 11 are made to communicate with each other through an oil passage 15s. Gear oil fed from an oil supplying device 30 provided in the vehicle body through a pipe 15a is discharged from the oil inlet path 15z into the speed reducing gear mechanism 11 to lubricate the gear of the speed reducing gear mechanism 11. Thereafter, the gear oil is guided from the oil passage 15s to the stator cooling path 10s to cool a stator coil 10c.”
In short, in this related-art technology, oil is supplied from the oil supplying device 30 to gears of the speed reducing gear mechanism 11, and to a stator coil 10c of the electric motor 10.
By the way, this related-art publication does not minutely describe actions of the oil supplying device 30, which, in fact, are not understandable. Since the abstract of the publication describes that the oil supplying device 30 is provided at the vehicle body side, it is considered that the oil pump 31 is probably not driven by the electric motor 10 or the speed reducing gear mechanism 11, but is driven by a control system of the vehicle body side, or the like. Therefore, in this related-art technology, it is necessary to monitor the state of the speed reducing gear mechanism 11 or the electric motor 10 of the in-wheel motor system, and to control the oil pump 31 so that it is driven according to the state thereof. Therefore, the control in the related-art technology is not easy to perform, and makes a complicated apparatus configuration.
On another hand, in Japanese Patent Application Publication No. 2004-180477 (JP-A-2004-180477), its abstract states “The drive unit for the rear wheel of a hybrid vehicle comprises an oil catch tank 71 for storing oil splashed by the driven gear 39 of a differential gear from an oil sump 69 formed at the bottom part of a casing body 11, a slinger chamber 61 being supplied with oil from the oil catch tank 71, and a slinger 65 disposed in the slinger chamber 61 and driven by means of a motor 15 through gears 68 and 67. In order to cool the motor 15, oil is supplied gravitationally from the oil catch tank 71 to the oil passage 31a in a main shaft 31 communicating with the interior of the motor shaft and oil splashed by the slinger 65 from the slinger chamber 61 is also supplied.”
In short, in this related-art technology, the oil splashed by the slinger 65 and the oil in the oil catch tank 71 are supplied to the motor 15 to cool it.
In the related-art technology of Japanese Patent Application Publication No. 2004-180477 (JP-A-2004-180477), the rotation direction of the driven gear 39 and the relative positional relationship between the driven gear 39 and the oil catch tank 71 are specifically determined so that the oil splashed by the driven gear 39 can be caused to enter the oil catch tank 71 when the driven gear 39 is rotating in the normal direction. Therefore, when the driven gear 39 is rotated in the reverse direction, it is impossible to cause oil to enter the oil catch tank 71.
Besides, in Japanese Patent Application Publication No. 2004-180477 (JP-A-2004-180477), oil is caused to flow into an inlet opening of the oil passageway 31a when the slinger 65 rotates in the normal direction. Hence, when the slinger 65 is rotated in the reverse direction by the motor 15, oil is caused to flow to a side away from the inlet opening of the oil passageway 31a, and therefore it is impossible to introduce oil into the oil passageway 31a. 
Thus, it can be said that in the related-art technology of Japanese Patent Application Publication No. 2004-180477 (JP-A-2004-180477), oil can be supplied to the motor 15 to cool the motor 15 only when vehicle forward travel power is output, and that oil cannot be supplied to the motor 15 when vehicle backward travel power is output.